Microfabricated fluidic systems are also being developed which employ nano-scale arrays comprising carbon nanotubes or other nanofeatures for use as separation matrices. One such example, utilizes nano-scale arrays of silicon pillars as separation matrices. However, the lithographic process at the nano-scale has been extremely difficult in the past. Other complications found in other on-chip separation device developments include, for example, the packing of columns with silica beads, which can complicate the fabrication process and drive up cost. Even highly efficient microfabricated devices such as those used for gas separation, still require that their columns be packed with carbon. If the packing process could be avoided, the microfabricated devices can be made more complex and more integrated.
One example which avoids the packing process is disclosed in the PCT publication number WO 01/63273 A2 to Noca et al, describing a molecular sieve employing self-assembled nano-arrays to separate molecules by differential transport therethrough via electrophoresis. The nano-arrays are fabricated using a template having germination points from which the nano-arrays are grown. As shown in the drawings, however, the template produces nano-features of uniform straightness and length which all have the same or similar orientations not intertwined or entangled with respect to each other. The “pores” in the Noca publication, therefore, are effectively defined by the spacing of the nano-features. While the Noca separation device is utilized to separate DNA strands traveling at different velocities through the device, the pore construction would be unable to also perform concentration or filtration functions effectively due to its large vertical pores that span the depth of the channel.